With such automatic production or assembly machines, an encounter of humans such as operators or service personnel for the automatic production or assembly machines with moving machines or machine parts may result in collisions that endanger the human and/or the functioning of the machine. When such an approach is detected early, or even in the event of contact, measures may be taken to prevent a collision, or at least to reduce the energy of the collision. This is often an important prerequisite for permitting the simultaneous presence of human and machine in the same work space.
For automatic approach and collision detection, monitoring of the surroundings of the machine may be conducted using various sensor principles and sensors, such as, for example, optical sensors, ultrasound sensors or capacitive sensors, or also using contact detection via the piezoelectric effect. Such sensors may normally be used in special cases, for example to monitor simply shaped machine parts having defined motion paths, so that, for example, when the approach of a human is detected, reliable deceleration of the drives or of the processing units of the machines may be triggered.
On the other hand, with relatively complexly shaped surfaces or a complex path motion of the dangerous machine part, consistent monitoring of the surroundings with the aid of sensors is often possible only using very great effort, or perhaps not even at all. For example, optical detection may be impeded at edges and undercuts of the machine surface by shading, or integration of sensors may fail due to lack of installation space.
For operator-safe machines it is customary, to fulfill safety standards, to employ safety devices having two mutually independent safety channels provided with diagnostic function, so that an individual error in the system does not result in loss of safety. The failure of one safety channel is reliably detected and reported, while the second safety channel maintains the safety function. Such applications require duplicate and independently executed monitoring by sensors. Sensors for reliable design of machines having two safety channels, which are flexibly adaptable to complexly shaped surfaces, are not known.
One potentially possible approach to collision prevention is to employ a protective fence in machines such as automatic assembly machines, so that the safety of the operator is ensured by forced separation of the human from the machine. In this case there may then be safe sluice gates present in the protective fence, for example for transferring parts. It is no longer possible to work directly together on an automatic production or assembly machine using such a protective fence, however, since the human and the machine cannot use the same work space at the same time here.
Another approach having a similar effect is known as two-handed operation, which only works when each hand of the operator is operating a pushbutton. In this case the pushbuttons are situated far enough outside the work space that any danger to the operator from the running machine is largely eliminated. In this approach, the human and the machine may use the same work space in principle, but not simultaneously. For example, the human and the machine cannot perform joint operating procedures.
German Patent Application No. DE 20 2005 002 475 U1 describes a foam covering which is equipped with proximity-detecting tactile and capacitive sensors, specifically for the application of collision detection in industrial robots. Mounting such a structure on different industrial robots is often complicated and expensive, however.